Real Time System

A Realtime System : A hydroelectric Power Station

Emergent System Properties

The name may seem to be quite frightening but the concept is not as difficult as the name sounds.

The easiest way to understand the definition is to break the term into 2 parts : Emergent and System.

Emergent comes from the word to Emerge, it means to arise from or stems from something.

Whereas a System can be defined as a purposeful collection of interrelated components that work together to achieve some objective. A system is composed of sub systems, modules and components. The characteristic of a sub-system is that they can operate as independant systems in their own right and they have specific properties.

When the sub-systems combine and work together as a whole new properties emerge from the system as whole and these properties are known as Emergent System properties. These properties cannot be attributed to any specific part of the system, rather they emerge only when the system as a whole is considered. The way these sub-systems interact with each other influences the successful functioning of the main system.

System Block Diagram

Functionalities of System

• Main Frame System

This is the mainframe computer system on which the software is set up and it is this computer that is reponsible for making descisions and carrying out these descisions.

• Water level sensor / River

A sensor is place in the river to detect the amount of water and the speed at which the water is arriving in the Dam. Readings are taken every hour in normal weather conditions. In case of flooding or bad weather the sensor detects the speed and amount of water every minute and transmits this information to the main computer which takes the necessary actions.

• River Door Controller

A mechanical device is implanted into the river to control the river gate. In case the mainframe computer decides from the sensor infromation it has obtained that the level and speed of water coming from the river is above normal values then as a precautionary measure it will activate the mechanism and shuts the river door.

• Water Level sensor in Dam

This sensor has as function to detect the water level in the Dam and send continuous readings to the mainframe system. In case the water level is too low or too high it is up to the main system to decide the appropriate actions to take.

• Blaster Door Controller in Dam

A mechanical device is implanted into the Dam to control the dam gate. In case the mainframe computer decides from the sensor information it has obtained that the level of water in the dam is below or above normal values then as a precautionary measure it will activate the mechanism and shuts or opens the dam door.

• Actuator - Emergency outlet

This emergency outlet found at the bottom of the dam is connected directly to the Main software. The mainframe will open this outlet in case that the level of water in the dam has gone above accepted values and release this water so as not to cause overflooding.

• Turbine Controller

A special mechanism used to control the turbine connected directly to the super computer. It is used to increase or decrease speed of the turbine depending on the time ; whether it is peak time or idle time.

• Water level sensor in Basin

This sensor detects the water level in the basin and sends the readings to the main PC whereby the latter will take the necessary actions.

• Evacuation outlet

The mainframe activates this outlet which is found in the basin in case of bad weather conditions and if the water level has gone above the normal level.

• Water pump

A special pump used to pump back water into the dam when there is a lack of water in the dam or in normal conditions at night. The system uses the electricity produced by the turbine itself to activate the pump.

• Siren / Telephone Caller

In case there is a system failure the siren is activated and an automated call is sent to the police station and fireman's department.

Emergent Properties

Functional properties : All parts of this system work together to achieve the objective of moving the turbine to produce electricity with the use of water.

Non-functional properties : Reliability, performance, safety and security. The system must be reliable in order to enable the proper function of all parts of the system. Performance must be at its maximum else the system will become unusable by its users if it is too slow. The system must also ensure safety and security for those using it, otherwise it will not be acceptable by users.

Sources of input from the Environment

• Water (level, speed and quantity)
  
• Weather which will determine the water level, speed and quantity.